Acoustic horn



pt. 17, 1929. H. B. ELY 1,728,480

ACOUSTIC HORN Filed Aug. 15, 1928 .Qwuentoz Hiram IE: E 1

mic mug Patented Sept. 17, 1929 UNITED STATES HIRAM B. ELY, OF PHILADELPHIA, PENNSYLVANIA ACOUSTIC HORN Application filed August 13, 1928. Serial No. 299,383.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1,928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The subject of this invention is an acoustic horn especially adapted for a sound locating apparatus employed in anti-aircraft gum nery.

In order to obtain accuracy, the acoustic 1 receivers of the present invention are horns having an exponential variation of cross section with the length, thus reducing reflection and consequent loss of sound energy while giving a maximum concentration or amplification. The amount of sound being reflected will be uniform and the disturbance to the entire system Will also be uniform and at a minimum.

Another provision making for efficiency consists in increasing the eflect of the lengt of the horn by doubling back the apical portion and attaching a flexible tube following the exponential form.

With the foregoing and other objects in view, the invention resides in the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

A practical embodiment of the invention is illustrated in the accompanying drawings,

wherein:

Fig. 1 is a perspective view of a sound 10- cating apparatus equipped with a group of the improved horns.

Fig. 2 is a view in side elevation of one of the horns.

Referring to the drawings by numerals of reference:

The acoustic horn is made up into rigid units of three sections, the ap'e'x jfi doubled 5 back against the mouth section'6 and these two are joined by a curved intermediate section 7. Attached to the apex of the horn is a fourth horn section 8, consisting of a flexible, reinforced tube, approximately equal in length to the reversely bent apical portion 5 and continuous with a flexible tube 9 which leads to the ear piece 10 of a head-set 11. The four sections of the horn throughout their length have a variation in cross section according to the simple, exponential equation A A 0c in which A=is the cross-sectional area at any point.

.go=is the cross-sectional area at a small en e is the base of the Naperian system of logarithms.

m is a constant determined by the rate of flare desired.

w is the abscissa measured along the horn axis from the small end as an origin.

In order to show the adaptability of the horn for grouping there is illustrated in Fig. 1 a sound locating apparatus of the trumpet type operating according to the system of binaural comparison in which the apparatus is directed at'the source of sound and the listeners, by reducing the phase difference to zero will receive the sound impulse in phase. The four horns of the group are rigidly interconnected in parallel and arranged in two combinations on intersectiong base lines which are constituted by a cross-arm support 12 whose horizontal axis is trunnioned in a pintle 13-mounted in a pedestal 14 which is secured to the platform of a carriage 15.

I claim:

1. An acoustic device for sound apparatus embodying a rigid horn composed of a mouth section, a curved intermediate section, an apical section 'disposed parallel to the mouth section and approximately the same length thereof, and a flexible tube attached to the apical section and approximately the same length thereof, and said horn and tube having an exponential variation of cross section with the length.

2. An acoustic device for sound apparatus embodying a rigid horn composed of a mouth section, a curved intermediate section, an apical section disposed parallel to the mouth section, a flexible tube attached to the apical section and approximately the same length thereof, and said horn and tube having an exponential variation of cross section with the length. i

HIRAM B. ELY. 

